The present invention relates to a new and distinct cultivar of Camptotheca, botanically known as Camptotheca lowreyana, and hereinafter referred to by the name `Katie`. The new Camptotheca is named in honor of Mrs. Katie Northrup of Houston, Tex.
Camptotheca, also known as Xi Shu or Happytrees, are deciduous trees, native to China, and a member of the Nyssaceae family. Three species of Camptotheca are significant sources of naturally-occurring camptothecins, a very promising anti-cancer chemical substance (Li et al., in press). The anti-tumor activity of Camptotheca was first discovered in 1957 (Wall et al., 1966). Clinical trials of camptothecins in the United States, China, Japan and Europe have shown success in treating may types of cancer (Li and Adair, 1994). Some camptothecin drugs have received approval for cancer treatment in more the 20 countries. Recently, three semi-synthetic drugs from camptothecins (Hycamtin, Campto, and 9-Nitrocamptothecin) were approved by the United State Food & Drug Administration for the treatment of ovarian, colorectal and pancreatic cancers. Camptothecins have also recently shown promise as inhibitors of HIV development in animal and human cell cultures (Priel, 1993).
Presently, production of camptothecins relies on Camptotheca trees. However, the production of Camptotheca trees is limited by low temperatures and drought. If new cultivars of Camptotheca that were more hardy and drought-tolerant were developed, the production of Camptotheca trees could be expanded.
The new Camptotheca is a product of a planned breeding program conducted by the Inventor in Nacogdoches, Tex. The objective of the breeding program is to create new Camptotheca cultivars that are more freely branching, have a higher camptothecin content and are tolerant to drought and low temperatues.
The new Camptotheca originated from a self-pollination made by the Inventor of the Camptotheca lowreyana Li (not patented). The cultivar Katie was discovered and selected by the Inventor within the progeny of the stated cross in a controllled environment in Nacogdoches, Tex., in April, 1995. The selection of this plant was based on its more freely branching habit, smaller leaf size, leaf shape, increased hardiness and tolerance to drought, and higher camptothecin content.
Asexual reproduction of the new Camptotheca by terminal cuttings harvested in a controlled environment in Nacogdoches, Tex., has shown that the unique features of this new Camptotheca are stable and reproduced true to type in successive generations.